Engines are designed to perform various functions such as power plants for vehicles and generator sets and in a variety of output horsepowers. Bore size, length of stroke and compression ratios are varied to produce different horsepower ratings.
Many of today's engines typically use a watercooled block made from one casting with a replaceable cylinder liner or integral bore within the block. U.S. Pat. No. 4,369,627 issued to Edward W. Kasting et al on Jan. 25, 1983 discloses an example of one such engine.
U.S. Pat. No. 1,226,820 issued to A. B. Shultz on May 22, 1917 discloses an engine in which the body comprises an upper base section, a lower base section and a cylinder section which are detachably connected with each other. The cylinder sections of this design has a water space which surrounds substantially the entire length of the cylinder from top to bottom. The Shultz patent requires a precisely aligned core to form the water space, an elaborate cleaning technique and a substantially full length cooling system from top to bottom of the cooled block portion requiring a large cooling system. The assembly technique used to secure the individual cylinders to the upper section is difficult to service and maintain because access to the fastening screws are located within the upper base section.
Some engine designs appear to be moving away from the full length water cooled block or cylinder liner in an attempt to increase efficiency, reduce cost and improve the emissions. For example, U.S. Pat. No. 4,294,203 issued to Philip E. Jones on Oct. 13, 1981 discloses an engine having an integral head and upper cylinder assembly for use with an integral crankcase and lower cylinder section assembly. The upper and lower assemblies are formed to receive a wet cylinder liner which is directly contacted by the engine coolant over only a portion of the exterior surface of the liner which is received within the upper assembly. Although eliminating the need for a large cooling system, the machining costs and complexity of operations have drastically increased overall cost. The casting process although simplified from Shultz's design still requires a complex core and cleaning process. A deep blind bore is required within the one piece integral head and upper cylinder section assembly to allow for inserting the cylinder liner therein. It has been found from past experience that the bottom portion of such deep bores cause stress concentrators resulting in cracks and failure of similar components such as cylinder liners and blocks.
The same type of area which forms stress concentrators can be seen in U.S. Pat. No. 4,305,348 to Martin issued Dec. 15, 1981 where the shoulder surface intersects the outer diameter of the cylinder liner. The addition of heat from the combustion chamber further compounds the stresses due to a lack of cooling available around or near the flange at the top of the liner.
The present invention is directed to overcoming one or more of the problems as set forth above.